An Introduction To Robots

The Binary Number System

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The basic parts of a computer are the central processing unit (CPU), memory, a keyboard or other input device and a screen or other output device. sounds simple, doesn't it? But how does the computer know how to add and subract, and how can its memory remember the answers it computes? We know that the computer doesn't have a real brain inside. It fact, it is made up mostly of plastic, metal and silicon. Yet, a computer acts in many ways as though it does have a real brain.

To find the answer, we must take a close look at how we understand numbers. We have ten digits in our number system: 0,1,2,3,4,5,6,7,8,9. Digit is a fancy word for a single number. It's interesting that digit also means a finger or toe. A number system based on ten is called a decimal system.

Computers don't use the ten digits of the decimal system for counting and arithmetic. Their CPU and memory are made up of millions of tiny switches that can be either ON or OFF. Two digits, 0 and 1, can be used to stand for the two states of ON and OFF. So we can see that computers could work with a number system based on two digits. This type of system is called a binary numbering system. How does this type of number system work? First, let's look more closely at our own decimal system. As you have learned in your arithmetic classes, our decimal system is based on place, or location. That is, the place of each digit tells you the value of that digit. For example, the number 17 has a 7 in the one's place and a 1 in the ten's place. In other words, 1 en plus 7 ones equals 17. The number 138 has a 1 in the hundred's place, a 3 in the ten's place, and an 8 in the one's place. Written in numerals this is (1X100) + (3X10) + (8X1)=138.

The binary system works in exactly the same way, except that its place value is based on the number two. In the binary system, we have the one's place, the two's place, the four's place, the eight's place, the sixteen's place, and so on. Each place in the number represents two times (2X's) the place to its right.

Here's a comparison of decimal and binary numbers:

Since the computer is really made up of tiny switches that can be either OFF or ON, you can look at a binary number as a series of light switches. A 1 represents a switch that is ON, and a 0 means a switch tha is OFF.

As you can see, numbers can become rather longin the binary system. For example, to show the number 10, we need four light switches, or four places. However, the real switches inside a computer are tiny and they are able to turn on and off very rapidly. The binary number system suits a computer extremely well.